30 CFR § 56.5001
Exposure limits for airborne contaminants.
AIR QUALITY
Except as permitted by §56.5005--
(a) Except as provided in paragraph (b) of this section, the exposure
to airborne contaminants shall not exceed, on the basis of a time weighted
average, the threshold limit values adopted by the American Conference of
Governmental Industrial Hygienists, as set forth and explained in the 1973
edition of the Conference's publication, entitled "TLV's Threshold Limit
Values for Chemical Substances in Workroom Air Adopted by ACGIH for 1973,"
pages 1 through 54, which are hereby incorporated by reference and made a
part hereof. This publication may be obtained from the American Conference of
Governmental industrial Hygienists by writing to the 1330 Kemper Meadow Drive, Attn: Customer Service,
Cincinnati, OH 45240; http://www.acgih.org
, or may be examined in any Metal and
Nonmetal Mine Safety and Health District Office of the Mine Safety and
Health Administration. Excursions above the listed thresholds shall not be
of a greater magnitude than is characterized as permissible by the
Conference.
(b) (b) Asbestos standard--(1) Definitions. Asbestos is a generic term for a number of asbestiform hydrated silicates that, when crushed or processed, separate into flexible fibers made up of fibrils. As used in this
part--
Asbestos means chrysotile, cummingtonite-grunerite asbestos
(amosite), crocidolite, anthophylite asbestos, tremolite asbestos, and
actinolite asbestos.
Asbestos fiber means a fiber of asbestos that meets the criteria of
a fiber.
Fiber means a particle longer than 5 micrometers ([mu]m) with a
length-to-diameter ratio of at least 3-to-1.
(2) Permissible Exposure Limits (PELs)--(i) Full-shift limit. A
miner's personal exposure to asbestos shall not exceed an 8-hour time-
weighted average full-shift airborne concentration of 0.1 fiber per
cubic centimeter of air (f/cc).
(ii) Excursion limit. No miner shall be exposed at any time to
airborne concentrations of asbestos in excess of 1 fiber per cubic
centimeter of air (f/cc) as averaged over a sampling period of 30
minutes.
(3) Measurement of airborne asbestos fiber concentration. Potential
asbestos fiber concentration shall be determined by phase contrast
microscopy (PCM) using the OSHA Reference Method in OSHA's asbestos
standard found in 29 CFR 1910.1001, Appendix A, or a method at least
equivalent to that method in identifying a potential asbestos exposure
exceeding the 0.1 f/cc full-shift limit or the 1 f/cc excursion limit.
When PCM results indicate a potential exposure exceeding the 0.1 f/cc
full-shift limit or the 1 f/cc excursion limit, samples shall be
further analyzed using transmission electron microscopy according to
NIOSH Method 7402 or a method at least equivalent to that method.
(c) Employees shall be withdrawn from areas where there is present an
airborne contaminant given a "C" designation by the Conference and the
concentration exceeds the threshold limit value listed for that
contaminant.
For further information: See MSHA's Program Policy Manual